I am developing a cost model for forging products. Can anyone give me direction on a good way to calculate the gross/net weight of a part from a print.
The best method is to get the part designer to include this data in the title block, since most of the solid modeling software being used for part design can calculate volume and mass (and surface area, for those heat treat guys).
The old standby method is to break up the part into goemetric shapes whose volumes can be easily calculated.
For a hollow tube, calculate the volume of a solid bar with the same OD and length, then subtract out the volume of the hole in the middle. If there's a flange attached, calculate its volume separately. If there's a tapered section, calculate that volume as the frustrum of a cone. Add the solids, subtract the voids, and make sure you don't double-dip (its easy to count a volume twice on complicated parts). Multiply the resulting part volume by material density, and you're done.
If you don't have your old high school geometry book handy, the Machinery's Handbook has a nice set of formulas for calculating these volumes. Alternately, there is freeware available for PCs and Palms to do these calcs as well.
Also this one. Calculates weight and volume of many different shape/material combinations, plus assemblies of different shapes, including shapes defined as cavities. Print and/or save data.
Look at this program. Calculates weight and volume of many different shape/material combinations, plus assemblies of different shapes, including shapes defined as cavities. Print and/or save data.